This invention relates generally to the field of telecommunications, and more particularly to a fused switch core and method for a telecommunications node.
The Internet has dramatically increased the potential for data, voice, and video services for customers. Existing circuit-switched telephony systems, however, do not provide the foundation to support the growing need for bandwidth and new services required by both residential and business consumers. As a result, integrated access devices have been introduced to support Internet and related technologies as well as standard telephony service for customers.
Integrated access devices often combine synchronous and asynchronous transport and switch functionality to multiplex data, voice, and video traffic together onto a single network. Within an integrated access device, a time division multiplex (TDM) bus is typically used to transport voice and other synchronous traffic between the line cards and a switch core. An asynchronous transfer mode (ATM) bus is used to transport ATM traffic between the line cards and the switch core.
At the switch core, ATM traffic normally arrives asynchronously while TDM traffic arrives in a regular and periodic fashion. To support switching of TDM traffic which includes synchronous transmission signal (STS-N) traffic and ATM traffic, the switch core typically uses multiple circuit cards each supporting one form of switching. These disjointed switch cards with separate data paths and switching hardware are expensive to implement and may be cost prohibitive for some lower-rate applications in which access devices are utilized. Moreover, the multiple circuit cards take up valuable space within an access device that could otherwise be used for line cards to support additional service interfaces.
The present invention provides a fused switch core and method for a telecommunications node that substantially reduce or eliminate the disadvantages and problems associated with previous systems and methods. In particular, the fused switch core provides tightly coupled time division multiplex (TDM), asynchronous transfer mode (ATM) and synchronous transmission signal (STS-N) switches that can be implemented on a single circuit card and that use a minimum number of integrated circuit devices.
In accordance with one embodiment of the present invention, a switch card for a telecommunications node includes a shared memory operable to store traffic channels. A time slot interchanger (TSI) is coupled to a first bus and to the shared memory. The time slot interchanger is operable based on predefined switching instructions to access the shared memory to store traffic channels received from the first bus and to retrieve traffic channels for transmission on the first bus. An ATM switch is operable to switch a traffic cells based on header information in the traffic cells. A traffic converter is operable to convert traffic channels retrieved from the shared memory to traffic cells for processing by a bus fuser to traffic cells and to convert traffic cells to traffic channels for storage in the shared memory. The bus fuser is coupled to the shared memory through the traffic converter, the ATM switch, and a second bus. The bus fuser is operable to receive a traffic cell from each one of the traffic converter, the ATM switch, and the second bus and to route the traffic cell to another one of the traffic converter, the ATM switch, and the second bus.
More specifically, in accordance with a particular embodiment of the present invention, the TSI, bus fuser, and ATM switch each operate at a synchronized frame pulse. The frame pulse matches a frame structure of the first bus and the second bus and may be a 125 microsecond pulse. In this and other embodiments, the shared memory may comprise a dual port random access memory (RAM). A bus merger may be provided to consolidate traffic from a plurality of point-to-point links for delivery to the bus fuser.
Technical advantages of the present invention include providing an improved switch core for a telecommunications node. In particular, the switch core fuses synchronous and asynchronous switching functionality together to support both synchronous and asynchronous traffic using a single circuit card. As a result, system space is optimized and costs are reduced.
Another technical advantage of the present invention includes providing a more scalable architecture for an integrated access device. In particular, a single fused switch card can be utilized in low speed applications to switch both synchronous and asynchronous traffic. The switch core can be supplemented with a high-capacity switch card for high-speed applications. Thus, the system cost is more directly proportional to functionality which allows low-cost solutions for low-rate and other limited applications.
Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, description, and claims.